Intravascular diseases are commonly treated by relatively non-invasive techniques such as percutaneous translumenal angioplasty (PTA) and percutaneous translumenal coronary angioplasty (PTCA). These therapeutic techniques are well known in the art and typically involve the use of a balloon catheter and a guide wire, possibly in combination with other intravascular devices. The balloon catheter is advanced over the guide wire such that the distal end of the balloon catheter is positioned adjacent a restriction in a diseased vessel. The balloon is inflated and the restriction in the vessel is opened, thus restoring normal blood flow.
While many PTCA and PTA devices are well known in the art, PTA has several unique technical and clinical challenges which prior art devices do not overcome. For example, typical PTA guide wire diameters range from about 0.018 inches to about 0.035 inches. The size of the guide wire used may depend on the preference of the physician, the desired vascular site, the morphology of the vasculature, the pressure monitoring capabilities necessary, the dye injection capabilities necessary and/or other device(s) to be used in conjunction with the guide wire. A physician may select or exchange several guide wire and catheter combinations to accommodate the diagnostic and therapeutic requirements of the procedure.
It is generally desirable to have a catheter which is matched to the specific size of the guide wire in use. The word matched in this instance means that the diameter of the distal end of the guide wire is about the same or just slightly less than the diameter of the distal end of the guide wire lumen. Matching the guide wire size to the catheter size avoids scraping, coring or carving vascular tissue when crossing a lesion or entering a puncture site without an introducer sheath. Scraping occurs when a catheter is used with an under-sized guide wire such that a circumferencial ledge is created between the guide wire and the distal of the catheter. The circumferencial ledge tends to scrape, core and carve vascular tissue creating unnecessary damage and increased potential for complications. To avoid these risks, a treating physician can match the catheter and guide wire sizes in order to minimize the circumferencial ledge. However, matching the catheter size to the size of the guide wire compromises the ability of the physician to take pressure measurements or inject contrast dye through the guide wire lumen with the guide wire in place. In addition, changing catheters or guide wires during the procedure increases the time and cost of the procedure. Thus, while a matched guide wire and catheter combination avoids the scraping problem, it increases the required time for a procedure, increases the cost of the procedure, compromises the ability of the physician to take pressure measurements and compromises the ability of the physician to inject contrast dye.
In view of the disadvantages of prior art catheters, it is desirable to have a single catheter which matches the size of a guide wire while maintaining the ability to measure pressure gradients and inject contrast dye with the guide wire in place. Such a catheter would minimize or eliminate the circumferencial ledge and thus minimize the resulting potential for vascular damage. In addition, such a catheter would eliminate the need to change catheters or guide wires and thus reduce the time and cost of the PTA procedure.